Wednesday, December 10, 2014

The Key to the Jon Lester: Jake Arrieta

One of the great things about this blog revamp is that I'm not longer beholden to only writing about the Twins. Here's my first non-Twins related blogpost.

By now, everyone has heard about the Cubs signing of Jon Lester to a 6-year, $155MM contract (with a $30MM signing bonus!) and I've seen numerous Cubs fans on Twitter now talking about how the Cubs are surely World Series bound. I love the optimism. I'm not here to squash those dreams but instead, I'm here to look at the Cubs rotation after Lester which, in my mind, leaves a lot to be desired.

One of the things I've been seeing on Twitter is this excitement surrounding a 1-2 punch of Lester and Arrieta. I understand the Lester excitement as he's been one of the best left-handed pitchers in MLB for the last several years. As for Arrieta however, he had a great 2014 campaign, but even a cursory glance at his numbers prior to 2013 makes one pause and perhaps pull back a little on the excitement about the Cubs #2 starter.

Arrieta was drafted out of college by the Baltimore Orioles in 2007. He rose fairly quickly with the Orioles and made his Major League debut in 2010 at the age of 24. He had been on the prospect radars but was never very highly ranked (#67 by Baseball America and #52 by Baseball Prospectus) so his arrival at the Big League level was quiet. During his rookie season he started 18 games for the Orioles compiling a 4.66 ERA over 100+ innings and had pretty lackluster peripherals including a 4.7 K/9 ratio, a 4.3 BB/9 ratio, an 89 ERA+, and a 4.76 FIP (5.17 xFIP).

Arrieta went on to miss parts of the 2010 and 2011 seasons due to bone spurs in his pitching elbow - a problem that was ultimately corrected via surgery in 2011. In 2012 Arrieta made the Opening Day roster but was mostly horrible through the first 3 months of the season before being demoted back to Triple-A at the beginning of July. In 2013, he again made the Opening Day roster, was again terrible, and was subsequently demoted to Triple-A again in Late April. It was at that point the Orioles decided to bail on Arrieta and they traded him to the Cubs. The Cubs gave Arrieta another shot in August of 2013 and he ended up pitching pretty well, compiling a 3.66 ERA over 9 starts to end the 2013 season.

Arrieta developed shoulder inflammation in Spring Training prior to the 2014 season and ended up missing the first 27 games of the year. His first start of the year was May 3rd and from then on, he was nothing short of spectacular for the rest of the season. He ended up giving the Cubs 156+ innings in 2014, had a sparkling 2.53 ERA, 0.98 WHIP (2.26 FIP, 2.73 xFIP) and had a stunning 9.6 K/9 ratio. I say stunning because prior to the 2014 season, Arrieta had a 6.9 K/9 ratio.

The biggest question with Arrieta is "was 2014 a fluke or did the Cubs change something in Arrieta's delivery, or arsenal, that contributed to this dramatic turnaround?" A few people in the blogosphere who are much better at explaining these things, have taken a stab at this question. In looking purely at the numbers, there are some indications that Arrieta made some significant changes and that his results from 2014 are something he can sustain into the future. The most significant difference you can see in the numbers is his lowered BB/9 rate. From 2010-2013, he walked an average of 4 batters per 9 innings. In 2014, he walked a mere 2.4 per 9. Another standout change is in the rate at which Arrieta induced ground balls. He has always been a ground ball pitcher, but he went from inducing ground balls about 43% of the time, to up around 49% of the time, or an increase of about 14%.

I took a look at Arrieta's PitchFX numbers (pitch speed) and his fastball averaged 93.4mph last seasons which is very typical of his entire career to this point...so a velocity change doesn't explain the different results. If you look at his pitch selection, however, one very interesting thing comes up. In his 3+ seasons prior to joining the Cubs, he threw his fastball roughly 60-65% of the time. In 2014, that number dropped to 47.5% of the time, and Arrieta added a Cut Fastball to his repertoire. That pitch, in particular, is probably the biggest reason for Arrieta's turnaround (in my opinion). Not only was that pitch worth a staggering 15.0 runs above average (stats courtesy of Fan Graphs), but the addition of a cutter made his regular straight fastball worlds more effective. Arrieta's swinging strike percentage went from being around 7% to north of 10%...this is, in large part, the reason he went from being a guy who had a K/9 around 7, to a guy with a K/9 rate of almost 10.

So, in summary, Arrieta with the Cubs has been a guy who walks less batters, strikes out more batters, induces more ground balls, has an improved arsenal of pitches and looks more like an Ace than a back-of-the-rotation pitcher. Now - having said all of that, I believe the jury is still out on Arrieta. One thing that can't be overlooked is his injury history. He had bone spurs with the Orioles, his Cubs career started out with shoulder discomfort and over the course of his career, he has yet to top 160 innings in a season (at the Major League level). He also only has one good season to hang his hat on. Maybe the cutter will change him forever. Or maybe he reverts back to the guy who walks a lot of guys. Either scenario is possible and until he has another great season, I don't think you say for sure, one way or the other.

In the ways that matter on the field, Arrieta really is the key to the Lester trade. If Arrieta continues to look like his 2014 self, the Cubs have a potential ace-ace 1 and 2 starter combo. If Arrieta reverts back to his old ways, then the Cubs have Jon Lester and a bunch of mid-rotation guys in Arrieta, Hammel, and someone chosen from the pile of Edwin Jackson, Travis Wood, Tsuyoshi Wada, etc. They also have Kyle Hendricks who is an intriguing young arm and who was impressive following his call-up in July, but who has yet to be tested in a full season at the Major League level.

A career-turnaround like Arrieta had in 2014 is impressive and the numbers and data provide many reasons to believe he is now a different pitcher. He's also pitching in the National League instead of the American League East which probably doesn't hurt either. For the Cubs' sake, I hope he continues with the success he had in '14. If he can, this Cubs team starts to look a whole lot more fearsome in 2015...World Series material even...